Energy Beamforming for Full-duplex Wireless Powered Communication in Presence of Eavesdropper

Abstract

To improve spectrum utilization, full duplex (FD) communication technique is applied to wireless powered communication (WPC). The cochannel interference from energy transmission reduces achievable rate of information transmission. However, when an eavesdropper tries to intercept the information in the FD WPC systems, the energy signal from the power beacon acts as a jamming signal to the eavesdropper. Hence, the secrecy rate of the system is not always degraded by the energy transmission. In this thesis, to control the energy signal transmitted to the source and eavesdropper, we propose an optimal beamforming scheme for secure communication in a FD WPC system consists of a multi-antenna power beacon, a source, a destination, and an eavesdropper. By using the beamforming scheme, the power beacon transmits an energy signal to a source which acts as a jamming signal to an eavesdropper and the source transmits an information signal by using harvested energy. We consider a scenario that the channel state information of eavesdropper is imperfect. We formulate an optimization problem to find an optimal beamforming for maximizing worst-case secrecy rate assuming that channel state information of the wiretap channel is imperfect. Also, we propose an algorithm to solve the problem. Simulation results show the secrecy performance of FD WPC system with the proposed beamforming scheme.